Reducing Uncertainty

The purpose of this exercise is to identify what parameters need to be further investigated if the current range of uncertainty in reserves is too great to commit to a development. In this example, the engineer may recommend more appraisal wells or better definition seismic to reduce the uncertainty in the reservoir area and the net-to-gross ratio, plus a more detailed study of the development mechanism to refine the understanding of the recovery factor. Afluid properties study to reduce uncertainty in (linked to the shrinkage... 

Keywords reducing uncertainty, cost-effective information, ranking sources of uncertainty, re-processing seismic, interference tests, aquifer behaviour, % uncertainty, decision tree analysis, value of information, fiscal regime, suspended wells, phased development. 

The stated objective of appraisal activity is to reduce uncertainty. The impact of appraisal on uncertainty can be shown on an expectation curve, if an outcome is assumed from the appraisal. The following illustrates this process. 

The choice of the location for well A should be made on the basis of the position which reduces the range of uncertainty by the most. It may be for example, that a location to the north of the existing wells would actually be more effective in reducing uncertainty. Testing the appraisal well proposal using this method will help to identify where the major source of uncertainty lies. 

Reservoir engineers describe the relationship between the volume of fluids produced, the compressibility of the fluids and the reservoir pressure using material balance techniques. This approach treats the reservoir system like a tank, filled with oil, water, gas, and reservoir rock in the appropriate volumes, but without regard to the distribution of the fluids (i.e. the detailed movement of fluids inside the system). Material balance uses the PVT properties of the fluids described in Section 5.2.6, and accounts for the variations of fluid properties with pressure. The technique is firstly useful in predicting how reservoir pressure will respond to production. Secondly, material balance can be used to reduce uncertainty in volumetries by measuring reservoir pressure and cumulative production during the producing phase of the field life. An example of the simplest material balance equation for an oil reservoir above the bubble point will be shown In the next section. 

The severe accident research program improved public risk assessment, reduced uncertainties, and the reliance on subjective expert opinion. To close two severe accident issues in NRC s Severe Accident Research Plan (NUREG-1365) Mark I Liner Attack and Direct Containment Heating (DCH) were addressed with a new approach using the Risk Oriented Accident Analysis Method (ROAAM) (Theofanous, 1994, 1989). The resolution of the Mark-I Liner Attack issue constitutes the first full demonstration of ROAAM. It emphasizes the determinism and provides a basis for synergistic collaboration among experts through a common communication frame. 

Confidence that the calculated failure rate is a good estimate of the true rate can be increased by lengthening the study or sample time. Adding another population of the same equipment under the identical circumstances to the original population will reduce uncertainties and increase confidence in the calculated failure rates. 

Making the Right Strategic Trade-Offs About Reducing Uncertainty... 

If it is already known at the pilot stage in which plant the final operation will be situated, solvent recycling, waste treatment, and utility supply processes should be modelled according to that specific plant. This reduces uncertainty in the scale-up from pilot to operation. 

OPPTS 860.1500, p. 16, indicates that 3-5 sampling points should be included in the decline trials. For applications close to the normal harvest time, the RAC may be harvested at selected intervals between the time of final application and a normal harvest or slightly delayed harvest. If the application is made long before the normal harvest, then representative plant tissues (including immature RAC) may need to be harvested in order to stretch the harvest period. A single composite sample is all that is required from each selected time point, but two or more samples may be harvested to reduce uncertainty about the actual amount of residue present at each sample time interval. These decline samples should be collected and treated the same as normal RAC samples. The samples should be frozen as soon as possible after collection. The instructions for decline sample collection and handling described in the protocol should be followed closely. 

Identifying and selecting improved tools to reduce uncertainties are one broad area where future research can benefit building evaluations. Other areas include ... 

Risk characterization provides a basis for discussions of risk management between risk assessors and risk managers (US EPA 1998). These discussions are held to ensure that results of risk analysis are presented completely and clearly for decision makers, thus allowing any necessary mitigation measures (e.g., monitoring, collecting additional data to reduce uncertainty, etc.). 

The rate of production analysis was complemented by a local sensitivity analysis and by a global Morris screening analysis. These analyses demonstrate the necessity of accurate measurements of j(0 D) and [HCHO] and reduced uncertainty in the quantum yields for H from HCHO photolysis. 

Can be translated relatively easily into emission profiles (reducing uncertainty in costs). 

Restrictions which may exist for the choice of a commercial reactor need not be imposed at the development stage. In some cases, a reactor of one type may be best for acquiring data in model characterisation, whereas a reactor of another type might be more suitable for full-scale production. (The cautions expressed in Sect. 4 must be taken into account.) Continuous flow back-mixed reactors can be very useful for kinetic studies because the absence of concentration gradients can reduce uncertainties in concentration measurements. When these reactors have attained a steady state, many of the problems associated with stiffness (see above) can be avoided. 

Difficulty in identifying what types of additional data are required to reduce uncertainty... 

Linkoff I, Burmistrov D, Kandlikar M, Schell WR. 1999. Reducing uncertainty in the radionuclide transport modeling for the Chernobyl forests using Bayesian updating. In Linkov I, Schell WR, editors. Contaminated forests. Dordrecht (DE) Kluwer, p 143-150. 

Person S, Long TF. 1997. Deconvolution can reduce uncertainty in risk analyses. In Newman M, Strojan C, editors. Risk assessment measurement and logic. Aim Arbor (MI) Ann Arbor Press. 

Practitioners of ecological risk assessments will frequently experience large uncertainty bounds on the estimates of risk. Unfortunately, characterizing and/or reducing uncertainty can be very costly. However, these costs must be balanced with the need to conduct sufficient analysis to make an informed decision. 

Reducing uncertainty is usually expensive. Therefore, an iterative process should be used to conduct the minimal amount of analyses that are necessary to characterize and reduce uncertainty to the point where an informed decision can be made. The point where a decision can be made with acceptable uncertainty will depend on the threshold of acceptability and threshold of unacceptability. ... 

Determine where additional data will reduce uncertainty the most. The process of Monte Carlo and Ist-order error analysis can help with sensitivity analysis and help to identify variables that need refinement and better data. 

Incertitude The kind of uncertainty arising from imperfect knowledge. Incertitude is also known as epistemic uncertainty, ignorance, subjective uncertainty. Type II or Type B uncertainty, reducible uncertainty, nonspeciflcity, and state-of-knowledge uncertainty. 

Strong public Improve focus on Improve focus on Reduce uncertainty Out of the corrective Team approach to... 

A typical illustration of a PAT approach to quality improvement is the use of near-infrared spectroscopy (NIRS) to qualify excipients and active principles just before they enter the production process, for example, in dispensing. As discussed in the next part, near-infrared (NIR) spectra are informative about product structure and overall quality. Because with substances such as excipients the quality range was investigated at some time in the past and fixed into a calibration, NIR measurement can provide simultaneous nondestructive confirmation of the predominant physical and chemical parameters. This is an effective method of reducing uncertainties about possible causes of failure or poor quality during production. Each time a given excipient fails its quality requirements at the moment of use, immediate action can be taken. Control is possible before the risk of failure is increased. Such an approach is complementary to container-wise identification of materials on delivery to a warehouse. 

We can reduce uncertainty by making more measurements. If we make 21 measurements and have the same mean and standard deviation, the 90% confidence interval is reduced from 0.0017to ts/Vn = (1.725)(0.0018)/V2T = 0.000 7 mL. 

Also special care should be taken to reduce uncertainties on emission data and measurements. The validation of an aerosol model requires the analysis of the aerosol chemical composition for the main particulate species (ammonium, sulphate, nitrate and secondary organic aerosol). To find data to perform this kind of more complete evaluation is not always easy. The same applies to emissions data. The lack of detailed information regarding the chemical composition of aerosols obliges modellers to use previously defined aerosols components distributions, which are found in the literature. Present knowledge in emission processes is yet lacunal, especially concerning suspension and resuspension of deposited particles [37]. 

Nowadays, highly sophisticated modelling approaches are available, which allow assessing PM at high spatial and temporal resolution, as needed for human exposure estimation. Thus no new models need to be developed (models predicting transport and transformation of aerosols in the atmosphere are available). Instead, methods need to be devised which are able to reduce uncertainty of modelled outputs. The respective results made available for a certain use allows understanding if answers to specific user questions can or cannot be supplied reliably. 

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